Three elderly people were abandoned by relatives in Hong Kong last year and abuse cases of the elderly increased 15 per cent to 368 - but a welfare group says this is just 'the tip of the iceberg'.

Against Elderly Abuse believes the figures underestimate the scale of the problem, although a spokesman for the Social Welfare Department says there is no sign of a long-term upward trend in the issue.

The department refused to give details of any of the cases but it is the first time since 2005 that more than one case of abandonment has been reported in a year.

Against Elderly Abuse says many cases go unreported. 'Because of Chinese culture, elderly people are reluctant to reveal the disgraceful affairs of their families,' said Roy Lam Man-chiu, the group's assistant executive director.

More elderly people are also being targeted by their children for cash, especially after adults received the HK$6,000 government handout for every permanent resident, announced in last year's budget.

Lam said victims were persuaded to hand over cash to sweet-talking children and some were assaulted after refusing to lend money.

'Last Christmas, an elderly woman complained that her son, who had failed to borrow money from her, removed her quilt and turned on a fan at high speed when she was sleeping,' he said. 'He was cold-blooded.'

The department said the number of cases involving abuse of the elderly went from 319 in 2010 to 368 last year. There were 465 reports in 2009 and 647 in 2008.

'The figures show that the elder abuse cases have fluctuated across the years and no significant uptrend has been observed,' a department spokesman said.

More than 70 per cent of last year's cases - 160 men and 208 women - involved physical abuse, while 12 per cent were related to money. Others involved psychological abuse, neglect and sexual abuse.

Two-thirds of the abusers were spouses, while 10.9 per cent involved their children and 11.4 per cent their domestic helpers. Other abusers included grandchildren, other relatives and neighbours.

The most high-profile abandonment case in recent years involved Tse Kam-wo who, in 2009, was left by his son in Guangzhou, where he had been taken to undergo cataract surgery. Then 75, Tse had his travel documents and HK$5,000 in cash taken, and he broke both his legs in a fall as he looked for his son. He was eventually helped to return to Hong Kong, and later said he had forgiven his son.

Against Elderly Abuse says such cases show the need for a dedicated law to cover abuse of the elderly.

But the department spokesman said there were already laws in force to tackle abuse. 'We do not see a need to enact dedicated legislation against elder abuse or for the protection of the legal rights of elders,' he said.